This invention relates to medical catheters for accessing vascular target sites for diagnostic or intervention purposes. In particular, this invention relates to micro-catheters capable of navigating through extremely small diameter vessels.
Goldsteen et al. U.S. patent application No. 08/745,618, filed Nov. 7, 1996 (which is hereby incorporated by reference herein), shows medical procedures and instrumentation for installing tubular grafts in a patient (e.g., for providing a bypass conduit around a blockage in the patient's circulatory system). A key aspect of that invention involves using flexible catheters that are inserted into a patient's body through remote entry ports. These catheters must be capable of traveling relatively long distances, sometimes through circuitous, small diameter vessels (less than 2 millimeters), such as peripheral vasculature of the brain and heart. This environment, however, may cause a guide wire located in the micro-catheter to bind, or cause the micro-catheter itself to kink or buckle, which may prevent the catheter from reaching a target site in a patient.
In addition to guiding wires, micro-catheters may be used to inject viscous fluids, including drugs, to target sites in the patient. However, due to the viscous nature of some fluids and the small diameter of the lumen of the catheter, the fluid may be injected through the lumen at very high pressures, sometimes as high as 400 psi. Such pressures may cause the wall of the micro-catheter to rupture, or burst, which may harm the patient. Also, these fluids may be reactive with the inner surface of the flexible micro-catheter, which may cause rapid degradation of the catheter wall, thereby increasing the susceptibility of the wall to bursting.
In view of the foregoing, it is an object of this invention to provide a micro-catheter to access vascular target sites for diagnostic and interventional purposes.
It is another object of the invention to provide a micro-catheter with improved kinking and buckling resistance.
It is still another object of the invention provide a flexible micro-catheter with high burst strength and relatively low reactivity with reactive fluids.
It is a further object of the invention to provide a flexible micro-catheter with a high degree of steerability.
It is yet another object of the invention to provide methods of manufacturing a micro-catheter that has variable flexibility and profile along its length.